The first time I visited the National Aquarium in Baltimore, I met a very angry frog.

It was a Budgett’s frog. He was only the size of a baseball, but when put on my white background, he did what Budgett’s frogs do: puff up, stand on all fours, growl like a mad cat, and try to bite with fangs embedded in the roof of their mouth. It would have been almost comical, if not for the fact that he could draw blood.

The aquarium has more than 16,500 animals. Of course I can only photograph a few, so I try to choose the most interesting ones I can. Most do not disappoint.

Recently I was accompanied by Claire O’Neill of National Public Radio’s Picture Show. We had only half a day, so we went for a few of the most interesting animals that the keepers thought would tolerate the portrait process.

First came an Amazon big-headed turtle, which didn’t move much (my favorite kind of photo subject). Next we had a prehensile-tailed iguana. If a predator tried to catch it in the wild, its extremely long tail would break off and wiggle—an elaborate distraction designed to let the body get away to fight another day. We also photographed walking sticks that moved in a rocking motion, simulating leaves on a branch in the wind. Perhaps the highlight of the day, though, were the seabirds: a razor bill and an Atlantic puffin in winter plumage. I made sure to photograph them last, because both are fish-eaters, and what they can do to a black velvet background isn’t pretty.

Departing wood frog (Rana sylvatica) at the National Aquarium in Baltimore, Maryland.